miR-199a functions downstream of MeCP2 in neurons of MECP2 duplication syndrome models

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Methyl-CpG-binding protein 2 (MECP2) duplication syndrome (MDS) is a severe neurodevelopmental disorder.
• The precise molecular pathology of MDS remains unclear.
• MeCP2 regulates neuronal functions partly through microRNA (miRNA) processing, including miR-199a.

Purpose of the Study:

• To investigate the role of miR-199a in the pathology of MECP2 duplication syndrome.
• To explore MeCP2's regulation of miR-199a in neuronal models of MDS.
• To identify potential therapeutic targets for MDS.

Main Methods:

• Generation and analysis of neurons from MECP2 duplication syndrome mouse models and patient-induced pluripotent stem cells (iPSCs).
• Assessment of neuronal morphology, synapse density, and mechanistic target of rapamycin (mTOR) signaling.
• Manipulation of miR-199a levels (inhibition and knockout) in MDS models.
• Analysis of human MDS cortical organoids.

Main Results:

• MDS neurons exhibited abnormal dendrite outgrowth, enlarged soma size, increased glutamatergic synapse density, and hyperactivated mTOR signaling.
• MeCP2 overexpression elevated miR-199a production in MDS models.
• Inhibition of miR-199a-5p improved soma size and mTOR activity; inhibition of miR-199a-3p normalized dendritic outgrowth.
• Genetic deletion of miR-199a-2 ameliorated synaptic and mTOR abnormalities in MDS mice.
• Suppression of miR-199a-5p reversed reduced neuronal activity in human MDS cortical organoids.

Conclusions:

• miR-199a acts as a critical downstream mediator of MeCP2 in the pathogenesis of MECP2 duplication syndrome.
• Specific miR-199a isoforms differentially contribute to MDS pathology.
• Targeting miR-199a offers a potential therapeutic strategy for MECP2 duplication syndrome.